Problem with USB numeric keypad on Latitude D820s

We have numerous models of Dell laptops that use our Terminal Server along with a numeric keypad for accessing our applications

 

Recently we bought 6 Latitude D820s for our Field Accountants. They are using different brands of USB keypads. 

 

The keypads work fine in normal Windows XP but when they log into our Windows 2003 Terminal Server the keypad does not work correctly.  The minus key, the triple zero key, the forward slash, and the enter key works. It’s just that we can’t use any of the numbers. 7 acts as the Home key and that is about it.  We’ve tried it with the numlock key on and off. I’ve tried moving it to another USB port and it still doesn’t work. 
 

The same keypad works fine on a different model Dell.

 

I am stumped as to why only this model of Latitude exhibits this problem.  Any ideas?

 

-Brett